Amylopectin adhesive

Amylopectin is the polymeric component of starch and consists mainly of glucose units joined at the 1,4-positions. Relative molar mass tends to be very high, e.g. between 7 and 70 million. A variety of modified starches are used commercially which are produced by derivatisation to give materials such as ethanoates (acetates), phosphates, and hydroxyalkyl ethers. Modified and unmodified starches are used in approximately equal tonnages, mainly in papermaking, paper coatings, paper adhesives, textile sizes, and food thickeners. 

Cellulose is a high molecular weight polymer of D-glucose with fi( 1 -4)-glycosidic bonds, found in plant fibres it is the major component of most plant tissues. Starch is another common polysaccharide, containing two polymers of glucose, amylose and amylopectin. It was used in some paint preparations and in the production of paper. Acid treatment of starch produces dextrins, which are used as adhesives and additives in water colour paintings. 

Esters from unsaturated fatty acid chlorides are usually viscous or limpid oils soluble in hydrocarbons and turpentine, and whose primary applications are as varnishes, films, artificial threads, aqueous emulsions, and rubber-like plastics.2067,2068 Heating them in an inert gas produced insoluble products formed by polymerization involving double bonds in the acyl moieites.2069 As mentioned in the section on nitrates, acetates of amylose are less compact than amylopectin acetate.1468 Esters of unsaturated acids have also been proposed as re-moistenable adhesives.1971 1972... 

The solid phase of bread crumb can be viewed as a composite material where amylose, amylopectin and protein form separated phases due to poor thermodynamic miscibility of the different polymers. Composites are characterized by exhibiting mechanical properties that cannot be achieved with the individual constituents alone, but are dependent on the interface between the components. A sharp interface as found between starch and protein provides strong evidence of little polymer interdiffusion and weak interfacial adhesion.14 The present results suggest that starch forms a continuous phase in bread which has also been confirmed with confocal scanning laser microscopy.15 The presence of a protein phase reduces the continuity of the starch phase and, thus, reduces the cohesion of the material as revealed by a comparison of the breaking stresses of aged flour and starch gels (data not shown).16... 

Although amylopectin is resoluble in water at room temperature, amylose is not. Starch adhesives are usually removed by swelling in water and scraping off the resultant gel. Even hot water is unlikely to dissolve amylose. Both enzymes (Daniels, 1995 van der Maarel et al., 2002 Schonbohm et al., 2004) and solvents such as Af-methyl-2-pyrrolidone (Green and Bradley, 1988) and dimethyl sulphoxide (Kurtzman et al., 1973) can be used to dissolve starch, but may in the process dissolve or disrupt other components of the substrate. 

Starch is a natural polysaccharide that can be derived from inexpensive and renewable resources. Starch films and coatings are primarily used for food packaging. Natural and modified starch films are also used to change the physical properties of food products such as soups and meat products by modifying the texture, viscosity, adhesion, moisture retention, and gel formation (Thomas and Atwell, 1997). Starch molecules are composed of two macromolecules namely amylose and amylopectin. Amylose has excellent film-formabihty, and forms odorless, tasteless, and colorless films. The relative amoimt of amylose and amylopectin depends on the plant source and is a key factor in determining the properties of starch. Generally starch contains 20-25% amylose and 75-80% amylopectin (Jimenez et al., 2012). 

Likewise, many of the adhesive properties can be explained by reference to the amylose and amylopectin properties of the starch used. Jelly gums are usually made from waxy starches (100% amylopectin) and are stable at room temperature for many months, as would be expected from the slow retrogradation rate of this starch. A corrugating formulation must set to form a bond and become water resistant in a short period of time. The low molecular weight portion of the amylose would be expected to come out of solution fairly rapidly to make a temporary bond, and the high molecular weight portion would more slowly tend to create water resistance. 

Starch - Starch can be derived from many plants including com, wheat, rice, and potatoes. It is composed of two polysaccharide forms - amylose (20%) and amylopectin (80%). Starch is water dispersable and widely used as an adhesive in paper packaging and wall papering. 

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